There is a low pressure system moving off the coast according to GFS between 20-21st. Trend is for it to move faster, that's why you see North wind. If it moves off the coast faster, say on 19th,it will be colder and the wind could be north west.

I think it's better if the forecast looks crappy this far out. It will either 1) allow me to wrap my brain around the reality of a windy rainy day and solidify my wardrobe choices (which are still completely up in the air), and B) any improvements as we get closer will feel all the more wonderful. Far worse to have a glorious perfect forecast this far out, and to watch it degrade day after day until we're left with

I'm sure I'm in the minority, but I'd actually prefer a 40 degree day with light rain to a sunny 60 degree day. The cool temps of Colorado have spoiled me. As long as it's not a torrential downpour, I actually like a light rain as it provides nice cooling (I'm sure my son and wife who will be waiting and watching are not in my camp on this one) . My big dread is a headwind. Although with the size of the crowds, it will surely make it easier to draft off of a group in front.

The NWS forecast discussion says there's a lot of uncertainty in the forecast for early next week. Given that, I think the best source right now for April 21 weather is RD's dog.

I should have known better and not peeked at this thread - I wasn't planning on getting sucked into checking weather until early next week. Sigh. There goes several hours of my life that could have been productive.

Ha! I love how often the meteostar website changes. At least twice a day!! (I guess it is also sad that I check at least twice a day). In other news, winds have shifted favorably.... for now.

It changes 4 times per day. But it is not a forecast. It is a run of a computer model. It runs every 6 hours.

They should use these computer models to forecast the weather. Maybe if they ran them every 6 hours, they could update the forecast 4 times per day.

They do. They actually use many different models and do averages. They also put more weight on models they feel perform better for certain regions, certain climates, and some models are just better than others. Also, they don't change forecast with just one model run, they weight for trends. Models do flip flop a lot.

I've got me a 7-day trial weatherbell.com account. Weather models galore. Still too far out. But if I were to summarize the Thursday-Saturday before the race in one word, the forecast is showing: cold.

The ECMWF is actually showing the possibility of about 3" of snow next Wednesday. (4" out by Worcester). WIth moderating temps until Saturday (52F Boston/56F Worcester). Tomorrow at this time we'll start getting two models for race morning... The extended GFS is calling for a high of 68F in Worcester on Sunday. 62F on Monday. 57F/52F in Boston. The extended GFS is so coarse it's useless...

I know. But I don't like seeing that....What do you see on those models for wind? My concern is that, if the weather is going to be warmer on Sunday and then cooler on Monday, it makes me believe that a front is going through that may bring some wind with it. If the wind is out of the west, then who cares. NNW isn't the worst, but it isn't good either.

It's way to early for wind forecasts. I think getting the temperature within 10F and whether it might rain or not is the best right now. I think by late tomorrow/Saturday will get a better picture. Next Monday will be way better...

It's way to early for wind forecasts. I think getting the temperature within 10F and whether it might rain or not is the best right now. I think by late tomorrow/Saturday will get a better picture. Next Monday will be way better...

ARRRGGGGGGG! Can I just bury my head in the sand for the next 10 days? Oh, what am I worrying about - it's just Boston.

It's way to early for wind forecasts. I think getting the temperature within 10F and whether it might rain or not is the best right now. I think by late tomorrow/Saturday will get a better picture. Next Monday will be way better...

I'm no meteorologist, but it seems that the wind direction is essential as it has a large bearing on the temperature and possible precipitation?

Does anyone remember when the first forecasts for the "heatwave" for race day in 2012 showed up on these long range weather forecasts? I don't even think they were predicting it that hot on the Friday before, but I might have hazy memory.

Re: 2012, the nws forecast discussion had a chance of heat about 7 days out and about 5 days out it was clear at nws (but not elsewhere) that it was going to be a bad day. That's why I try not to look until 7 days out, and don't get too excited about anything I'm seeing until a couple days later.